Piston and packing



Jan. 25, 1944. K A. B. ROOT, JR 2,339,949

` 6- kVf k i6 Jan. 25, 1944. A.. B. RooT, .JR

PISTON AND PACKING Fl'ed June 7, 1941 2 Sheets-Sheet 2 Inveno: B. Roo?. Jzfr,

Patented Jan. 25, 1944 PISTON AND PACKING Albert B. Root, Jr., Newton, Mass., assigner to Hunt-Spiller Manufacturing Corporation, Boston, Mass., a corporation of Massachusetts Application June 7, 1941, serial No. 397,057

(ci. aos- 29) 3 Claims.

This invention relates to pistons having segmental metallic packing rings spring-pressed into contact with the cylinder wall, and the object is to provide a construction wherein the full eifect of the spring on the several segments of the packing is at all times availed of in use.

My invention will be well understood by reference to the following description taken in connection With the accompanying drawings, wherein by way of example I have shown a piston and packing as used in the horizontal cylinder of a steam locomotive and wherein:

Fig. 1 is an edge view of a locomotive piston and its packing rings;

Fig. 2 is a diametrical section on the line 2-2 of Fig. 3, the central portion of the piston being broken away; and

Fig. 3 is a transverse section through the piston at the location of one of the ring grooves, the ring being omitted.

In many applications of pistons they normally take up a position eccentric to the cylinder in which they work and the packing rings therefore project further on one side than on another. A notable example is in the case of a horizontal cylinder as in the case of a steam locomotive wherein the center line of the piston is displaced under gravity downwardly relative to the center line of the cylinder. Herein for convenience and clearness I will refer to such a horizontal piston as representative of the class first referred to and use the words upper, lower and the like, lower, for example, referring to the side of the cylinder toward which the piston is normally displaced.

Referring now to the drawings, I there show a piston 4 having a pair of ring-receiving grooves 6 receiving piston rings 8, these rings each comprising two series of segments laterally adjacent, the segments in the respective series being staggered. The construction may be generally similar to that disclosed in the patent to Platt, 1,643,628. In the drawings, however, I have illustrated these rings as being of the type commonly referred to as lip rings, the outer portions of the segments having laterally extending anges or lips I0 which overlie the outer face of the piston adjacent the grooves. ence or absence of these lips, however, is not of controlling importance in connection with the present invention. They are an example of a construction wherein the lower segment of the ring may support the weight of the piston. Another example would be one wherein the radial depth of the ring, or the combined depth of the 'I'he presvil) ring and an underlying spring, exceeded the depth of the groove.

Each ring 8 is supported by a spring I2 in the form of a divided or split ring (see Fig. 3) which underlies `the segments rand normally presses them radially outwardly. Herein the ring I2 is shown as received in its entirety beneath the segments and Abeing of substantially the same width. The groove 6, therefore, in the example shown is of generally rectangular cross section and of su'icient depth to accommodate the spring and the bodies of the segments.

It is desirable that in use the segments of the packing ring be free to rotate relative to the piston to distribute the wear. In certain types of segmental packing rings provision has been heretofore made to lock the supporting spring to the ring segment in such a manner that no relative circumferential movement as between the ring and the springs has been possible. In other constructions wherein such interlock between the spring and the ring is not provided for, the spring and ring probably have relative movement circumferentially with respect to each other and the spring, of course, can move relatively to the piston either with the ring segments or differentially thereto.

Referring now to Fig. 2, the piston and its packing are there shown in the position taken in use when the packing is restrained by the cylinder wall. The piston body settles under gravity until it is supported at its lowermost point by the packing. In the example illustrated the lipsl seat on the piston face and the bottom of the segments seat on the spring I2 which in turn rests on the bottom of the groove 6. At the upper portion of the cylinder the piston face is correspondingly retracted from the cylinder wall and the segments 8 must therefore be pressed out by the spring I2 to engage the wall in the manner indicated in the drawings. A similar condition in varying degree is found at lother portions of the circumference.

Let us suppose now the split of the spring I2 to be at the bottom of the cylinder, that is, in such a position as would be indicated by turn.- ing Fig. 3 upside down. The ends of the spring I2 are then subject to being clamped by the overlying segment of the packing and in that case the spring would become essentially an unbroken circle and the resultant supporting effect, notably at the upper side of the piston, be severely limited. In an intermediate case corresponding, for instance, to a rotation of Fig. 3 clockwise through an angle of 90 with the break between the ends of the spring displaced to three oclock position, the portion of the spring then at the bottom of the cylinder may be similarly clamped, leaving at the right a short, relatively inflexible arm, while the effective supporting action of the spring at the top of the cylinder would be restricted to one arm thereof.

In accordance with my invention I therefore provide means for locking theyspring I2 in the groove 6 with the break between the ends of the former permanently positioned at the upper portion of the piston while preserving the freedom of movement of the segments Vin the groove. Herein I have shown this as effected by providing at the central portion of the spring 'I2` 0pposite the split an inwardly projecting pin or stud I4 adapted to enter a hole drilled to receive the same in the bottom of the piston ring groove at such a point that when'the'pi'ston'isv applied to the cylinder the hole shall be -at the bottom of the cylinder. Other means for preventing circular rotation of the ringl within the piston ring grooves obviously may beprovided.

` With this construction, asis seen by reference to Figs. 2 and 3, those segments of the packing ring at the top ofthe cylinder which have the greatest range of movement and require the most efficient support receive it fromI the two ends of the spring and its resilient reaction is proportioned to the demands thereon at other parts of the circumference.

It may be noted that in Fig. 3 I have not attempted to showV the spring I2 expanded but rather in the position in which it would beheld by the packing ring when the piston is in the cylinder, although the ring itself is not shown in the figure.

I am aware that the invention may be embodied in'other Vspecific forms without departing from the spirit or essential vattributesy thereof,

and I therefore desire the present embodiment to be considered in all respects as illustrative and not restrictive; reference being had to the appended claims rather than to the foregoing description to indicate the scope of the invention.

I claim:

1. A piston for horizontal operation having a ring-receiving groove, a packing ring therein formed of .a number of segments, a spring in the form of a vdivided ringbeneath thesegments, the spring and ring as an assembly having a radial depth greater than the depth of the groove whereby the ring may support the weight of the piston, and means independent of the segments forpostioning the spring with the division point thereof at the' upper portion of the piston.

2. A Apiston for horizontal operation having a ring-receiving groove, a packing ring therein formed of a number of segments and being free for circumferential movement in the groove, a divided spring ring supporting the segment, the springring and packing ring as an assembly having; av radial depth greaterV than the depth of the groove whereby the ring may supportI the weight of the piston, the spring ringv havingits central portion secured against circumferential move.- ment to the piston body adjacent the lowermost portion thereof.

3.`A piston for horizontal operation having a ring-receiving groov,"an incompletely annular spring in the groove,` means for positioning the same to locate "its ends at the top' of thepiston and circumferentially movable packing Vring segmentsl in the groove and overlying the spring, the` spring andv ring as an assembly havingl a radial depth greater than the depth of the' groove, whereby the ring may support the weight ofthe piston."

ALBElRT B; ROOT, JR. 

